An "urban" community now must have at least one neighborhood with a density of more than 1,000 residents per square mile as well as a total population of at least 2,500, Henrie says. Every neighborhood in the designated urban area must have at least 500 residents per square mile -- except for parts of town covered by airports, malls or other urban-type places where people don't live.

Not surprisingly, Portland, Eugene, Salem and Bend all are considered urban. They are home to 84,000 to 1.8 million people, and each is home to an average of more than 2,000 people per square mile. The Portland urban area, stretching to Vancouver, Hillsboro, Gresham and Oregon City, has about 3,500 people per square mile spread over 524 square miles, the bureau reported.

Nearly matching that density, however, is the small town of Canby -- a historically agricultural community of about 17,000 people 20 miles south of Portland that was designated rural in the 2000 Census. Not anymore, the bureau says.

Canby has attracted several manufacturing employers, including several that export their products internationally, and it is seeing a mini-boom in new home construction after a lull during the recession, reports the city's economic development director, Renate Mengelberg.

View full sizeJamie Francis / The OregonianWhen a tornado struck downtown Aumsville in December 2010, volunteers turned out to help. The only business destroyed in the disaster is just about to reopen in the close-knit small town. The Census Bureau calls it urban, and in some ways, city administrator Maryanne Hills agrees.

Still, it remains a place where high school sports events are the center of town life, where folks greet each other on the sidewalks of downtown and where anybody can sign up to drive their tractor in the annual General Canby parade, says Canby Library Director Penny Hummel.

"Do I think of it as half as dense as Los Angeles? No I don't. It's a classic small town," Hummel says.

In the eyes of the Census Bureau, Oregon has more "urban" areas per mile on its Pacific coastline than Washington or California, including Gold Beach, Bandon, Waldport, Reedsport and Seaside.

In stoplight-free Aumsville, population 3,680, the vibe is know-your-neighbor, small-town safe. Every year, "Santa" rides the city fire truck to every home in town to offer a goody bag to the city's young and young at heart.

Still, says city administrator Maryanne Hills, "urban" areas like Aumsville are distinctly different from the rural areas that surround them. Aumsville has police coverage, two developed city parks and, unlike their septic-system country cousins, "a water and sewer system they can depend on... You have the urban benefits of the city."